Vehicle brake



Feb. 24, 1942.

J. H. PRATT Er AL VEHICLE BRAKE Filed "June 27, 19:59

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Feb. 24, 1942. J H R T 2,274,213

' VEHICLE BRAKE Filed June 27, 1939 3 Sheets-Sheet 2 Feb. 24, 1942.

' J. H. PRATT Er AL.

VEHICLE BRAKE Filed June 27, 1939 3 Sheets-Sheet 3 Patented Feb. 24, 1942 James Henry Pratt, Gilbert Edgar Manll y, and Albert Henry Godfrey Girling, Birmingham,

England 1 Application June 27, 1939, Serial No. 281,404 g In Great Britain'July 8,1938

' 4 Claims. (Cl. 188-72) This invention has reference to improvements relating to vehicle brakes of the disc type and has for its object the provision of an improved vehicle brake of the said type which is robust in construction, eflicient in use, capable of being readily adjusted, when in position and which possesses a degree of self energising braking effort in each direction of movement.

The invention consists of an improved vehicle brake of the disc type which is characterised in that there is interposed between a movable clamping means and a relatively fixed member movable means a movement whereof obtains when the movable clamping means is brought into contact with the disc during turning of the disc whereby the said movable means is caused to exert an increased clamping effort on the aforesaid movable clamping means thus introducing an additional braking effort by self energisation.

The inventionalso resides in an improved vehicle brake of the disc type in which adjustment to compensate for'wear can be made by the manipulation of means which is capable of being'actuated from the outer side of the brake when in position.

The invention further resides in the means for actuating the movable clamping members in brakes of the disc type whereby the said movable clamping members are caused to engagethe respective discs inplanes which are oblique to the direction of travel.

The invention still further resides in the details of construction of the improved vehicle brake of the disc type to be described hereinafter.

A convenient embodiment of the invention will now be described with particular reference to the accompanying sheets of drawings which illustrate the invention in its application to a disc brake for use with very heavy motor vehicles.

In thedrawings:

Figure 1 is a vertical section of the improved disc brake. I

Figure 2 is a rear view of the brake illustrated in Figure l with some of the upper parts removed for the sake of clearnes's.

Figure 3 is a fragmentary view'of a lever operated means for actuating the movable member of the brake.

Figure 4 is a fragmentary view of a hydraulic means for actuating the movable member of the brake,and Figure 5 is a fragmentary view of a modified I means of mounting the interposed movable .means.

Like numerals of reference indicate similar parts in the several views.

According to the embodiment of the invention illustrated the wheel 6 has bolted thereto adjacent its periphery the vertical limb I of an annular carrier plate, referred to generally by the reference numeral I, of a substantially right angle shape in cross section, the horizontal limb l of said carrier plate I being arranged'on the inner side of the wheel 6. Adjacent the end the horizontal limb l of the said carrier plate I is provided with a plurality of equidistantly spaced slots 1 within which are engaged correspondingly arranged projections 8 which project outwardly from the periphery of a metallic disc, 9 which constitutes the braking disc so that the disc 9 is capable of a floating movement toward and away from the carrier plate 'I but is always incapable of rotary movement relatively thereto. The brake disc 9 has fixed thereto on each side a block I0 of friction material which is preferably moulded on to the disc. The faces of the blocks In of friction material co-operate with clamping members I I, I2 the outermost of which,

namely II, will be referred to hereinafter as the fixed clamping jaw I I. This fixed clamping jaw I I is in the form of a heavy cast iron ring which is splined on a central portion I3 which is bolted to a fixed part of the axle casing I4. At a convenient point the fiange of the wheel 6 is provided with an opening through which may be passed a tool I5 bearing adjacent its end a pinion I5a. The inner end of the tool I5 is constituted by a short cylindrical spigot I5 The fixed clamping jaw II is provided with a cylindrical hole II for the reception of the spigot I5 and with a gapped portion I I for the accommodation of the pinion I 5 The teeth of the pinion I5 are adapted to mesh with teeth I (i formed around the periphery of an annular locking ring I6 which is adjustably mounted on a screw threaded portion l3 of the central portion I3, so that by engaging the spigot I5 in the hole Il and the pinion I5 in the gapped portion II with the teeth of the said pinion I5 in mesh with the teeth IIi and rotating the tool I5 the locking ring I6 may be adjusted on the central portion I3 for determining the position of the fixed clamping jaw I I relatively to said portion for adjusting the positionof the fixed clamping jaw I I relatively to the presented faces of the blocks Ill carried by the disc 9in order to compensate for wear when necessary. The co-operatingclamping member I2 which will be referred to hereinafter as'the an annulus which is provided on its rear face and in the upper half thereof with a plurality of conically sided pits l2 which are complementary to similar conically sided pits M formed in the adjacent face of a peripheral flange |4 forming part of the axle casing l4. Located Within each pair of pits l2 M is a bearing ball I8, and the Walls of the pits I2 I l are normally held in contact with the periphery of their respective.

balls l8 when the brake is out of action by adjustable springs l9 operating through struts 20 having ball ends 20 which co-operate with complementary seatings formed in the movable clamping member l2, the said springs l9 also tending to hold the movable clamping member l2 out of the clamping position when the brake is required to be out of action. 7

The movable clamping member i2 is adapted to be operated by a bowed lever 2| which is fulcrummed on knife-edges 22 arranged symmetrically on either side of the casing l4 in the lower half thereof, the lower end of the bowed lever 2| being pivotally connected to a rod 23 which in turn is connected to the brake applying means (not shown). The bowed lever 2| co-operates with ball ended struts 25 which transmit movements of the said bowed lever 2| to the movable clamping member [2 when the brake is to be applied manually.

. In place of, or in addition to, the bowed lever 2| the brake may be applied by moving the movable clamping member l2 by hydraulic means, which as illustrated in Figure 4 comprises a hydraulic cylinder 26 carried by the flange M having therein a piston 27 which actuates the movable clamping member I2 through the agency of a ball ended strut 28.

Two of these hydraulic devices would be utilised in the embodiment of the invention illustrated and they would be located adjacent the pointswhere the bowed lever 2! applies its braking force.

It is found that during a braking operation with the disc 9 turning, when the friction face of the'movable clamping member l2 contacts with the friction face of the block H] the balls I8 run up the sides of the respective pits i2 M and provide a self-energising braking effort, the degree of which is found to be determined by the angle of inclination of the sides of the pits l2", M a convenient angle being 40. The balls l8 are located in the upper portion of the movable clamping member l2, whereas the springs l9 that return the clamping member l2 to its inoperative position when the brake is released are equally spaced around the clamping member |2. Thus the resultant of the force exerted by the wedging balls I8 is substantially displaced from the resultant of the force exerted by the releasing springs -|9.

Moreover, it will be seen that the self-energising effort acts equally in each direction of rotation and that the relatively heavy mass of the clamping members I I, I2 and the parts which carry these members results in the brakes operating under cool conditions. The cool operation of the brakes is further enhanced by forming holes in the central portion of each wheel and in the carrier plate 1 which provide for the circulation of a current of air through the brake as a whole.

It should also be appreciated that upon application of the braking pressure with the disc 9 turning the said movable clamping member I2 is caused to engage the said disc 9 obliquely,

which oblique movement again is found to exert a powerful self-energising effect. It is found that a useful degree of self-energising braking effort so obtainable is increase of the braking force resulting directly from the operation of the brake actuating means with the disc 9 turning. The obliquity is the product of movement produced by the perpendicular movement resulting from the drivers control and the circumferential movement resulting from disc rotation.

In the case of a brake for light vehicles only a pair of balls I8 are required and these may be located in pits arranged in the upper half of the brake in positions corresponding to the positions at which the braking effort is applied in the lower half.

In the modification illustrated in Figure 5, instead of forming the pits i2 and M in the movable clamping member l2 and the flange M the conical faced pit associated with the movable clamping member I2 is formed in a separate annulus 29 having in the centre thereof a conically seated recess 2%, whereas the conical faced pit associated with the flange M is form d as a conical recess in the inner end of a plug 30 adaptedto screw into a hole in the said flange M a nut 3| being provided for locking the screw plug in the opposite position.

What we claim is:

l. A brake of the disk type for a vehicle wheel comprising, in combination, a friction member rotatable with the wheel, a second friction member, a non-rotatable thrust-receiving member adjacent the second friction member, energizing means actuated by rotation of the second friction member relative to the thrust-receiving member for thrusting the second friction member toward the first friction member, the force exerted by said energizing means being applied at points substantially to one side of a plane passing through the axis of rotation, yieldable means for normally thrusting the second friction member away from the first friction member, the force exerted by said yieldable means being distributed with substantial uniformity on both sides of said plane, and brake-applying mechanism operable at will for overcoming the force exerted by said yieldable means to bring the friction members into engagement, the force exerted by said brake-applying mechanism being applied at points substantially to the other side of said plane.

2. A brake of the disk type for a vehicle Wheel comprising, in combination, a friction member rotatable with the wheel, a second friction member, a non-rotatable thrust-receiving member adjacent the second friction member, opposed conically sided pits in the adjacent faces of the thrust-receiving member and the second friction member, all located substantially to one side of a plane passing through the axis of rotation, balls in said pits for thrusting the second friction member toward the first friction member upon rotation of the second friction member relative to the thrust-receiving member, yieldab-le means for normally thrusting the second friction member away from the first friction member, the force exerted by said yieldable means being dis tributed with substantial uniformity on both sides of said plane, and brake-applying mechanism operable at will for overcoming the force exerted by said yieldable means to bring the friction members into engagement.

3. A brake of the disk type for a vehicle wheel comprising, in combination, a friction member rotatable with the Wheel but capable of axial displacement, a fixed central support, a second friction member rotatable upon said support at one side of the first friction member, a third friction member splined to said support at the other side of the first friction member, a locking ring threaded on said support outside the third friction member and having gear teeth by which it may be rotated, means for locating a tool inserted from the outside to rotate said locking ring, a non-rotatable thrust-receiving member adjacent the second friction member, energizing 4. A brake of the disk type for a vehicle wheel comprising, in combination, a friction member rotatable with the wheel, a second friction memher, a non-rotatable thrust-receiving member adjacent the second friction member, opposed inserts in the adjacent faces of the thrust-receiving member and the second friction member, all located substantially to one side of a plane passing through the axis of rotation, conically sided pits in said inserts, balls in said pits for thrusting the sec-0nd friction member toward the first friction member upon rotation of the second friction member relative to the thrust-receiving member, yieldable means for normally thrusting the second friction member away from the first friction member, the force exerted by said yieldable means being distributed with substantial uniformity on both sides of said plane, and brakeapplying mechanism operable at will for overcoming the force exerted by said yieldable means to bring the friction members into engagement.

J AlVLES HENRY PRATT. GILBERT EDGAR MANLEY. ALBERT HENRY GODFREY GIRLING. 

